High Performance Roofs How to Beat the Heat

Transcription

1 High Performance Roofs How to Beat the Heat H. Akbari, P. Berdahl, R. Levinson, INDUSTRY COLLABORATIVE R&D LBNL CEC Chris Scruton DOE BT Marc Lafrance Building Envelope Program Oak Ridge National Laboratory W. Miller, J. Kosny, T. Stovall, A. Karagiozis D. Yarbrough, A. Desjarlais

2 OBJECTIVES 1. Merge strategies into Next Generation Attics Cool color roofs Ventilation Radiant barrier Thermal mass 2. Energy impact of alternative attic ventilation schemes 3. Energy benefit of thermal mass (PCM) 4. Consensus based calculator ESRA

3 WHAT ARE COOL COLOR ROOFS? Cool color, sub-tile venting and thermal mass concrete and clay tile Key Find: Cool color and sub-tile venting eliminated 70% of peak heat transfer penetrating roof deck (asphalt shingle control) Demonstration homes showcasing cool color medium profile concrete tile (Hanson Roof Products) and painted metal shakes (Custom-Bilt Metals) Key Find: Cool color roofs reduced summer electricity 3 to 5% Demonstration homes with cool color asphalt shingles (GAF/ELK Group) Key Find: Peak shingle temperature drops 3 C (5.4 F)

4 COOL COLOR PAINTS ARE HIGHLY REFLECTIVE IN INFRARED SPECTRUM

5 CAMOUFLAGE INVISIBLE TO IR NIGHT VISION Conventional Film Near Infrared Film

6 Cool Tile IR Coating TM Applied to Concrete Tile COOL TILE IR COATING technology was developed by Joe Reilly of American Rooftile Coatings

7 S-Mission Tile Have Lowest Heat Transfer Penetrating the Roof Deck 1:30 PM

8 Demonstration Showcasing Painted Metal Shakes at Fair Oaks, CA ORNL Custom-Bilt Painted Metal Shakes and Stucco South facing roof House Mariah Place Ultra Cool 31% reflectance House Mariah Place

9 Cool Coating Reduces Heat Flux Through South Facing Roof Deck Painted Metal Roofs

10 Demonstration Showcasing Hanson Concrete Tile at Fair Oaks, CA Finished with Medium-profile Concrete Tile and Stucco House Mariah Place COOL COOL TILE TILE IR IR COATING 41% reflective House Mariah Place

11 Medium-profile concrete tile Same setup used at Fair Oaks Demonstration Batten Direct-to- Deck Batten and Counter-Batten (ESRA) Envelope Systems Research Apparatus

12 Medium-profile conventional concrete tile on double batten performs as well as cool-color tile direct-to-deck

13 Fair Oaks Demonstrations Show Positive Benefits of Cool Colors

14 Squares of Roof Products F.W. Dodge Report 2003

15 Hurdle: optimize reflectance of Cool Shingles and Stone Coated Metals

16 Demonstration Homes Provided by Elk Corp and Ochoa & Shehan Custom Homes SR ~ SR ~ Eel Street, Redding CA 2605 Loggerhead St., Redding CA

17 Heat Flux Penetrating West Roof Reduced 25% of Conventional Shingle

18 110 Million Existing Homes in U.S. that Require Improvements in Building Envelope Retrofit Shingle Roof Tooth Surface LP TechShield Top Temperature ( o F) Outdoor air Underside LP TechShield Air gap Top Tdeck EPS Underside of Tdeck EPS Center Cavity Conventional Attic Time (hrs) Envelope Systems Research Apparatus

19 WHAT ABOUT ROOF/ATTIC VENTILATION? Develop empirical algorithms to capture energy benefits of above-sheathing ventilation Status: heat transfer correlations checked against field data, tracer gas used for airflow measures, algorithm formulated & validated MCA installing stone-coated metal roofs on ESRA

20 Clay tile, concrete tile, painted metal shake, asphalt shingle, and stone-coated metal roofs field tests Formulate and Validate AtticSim for Cool Color and Above-Sheathing Ventilation ESRA

21 Attic Assembly Construction and Instrument Setup

22 ASV Reduced Heat Flow Crossing Deck by 30% of Asphalt Shingle August 2005

23 Deck Heat Flow Reduced 45% by IRR pigments and ASV Above Sheathing Ventilation SR increase of 0.17 ~ 30% of control ~ 15% of control Q Attic vent Q HFT Roof Deck COS( ) Q HFT Attic floor Q Deck vent Q Solar Abs Q Mass COS( ) Q HFT Roof Deck

24 Above-sheathing ventilation accelerated the removal of unwanted moisture reduced moisture content in OSB well below that of OSB in a non-vented cavity 2-D MOISTURE-EXPERT model (Karagiozis)

25 Next Generation Prototypes Milestones ( ) Regional Criteria for Above-Sheathing Ventilation Develop Recommendations for above-sheathing Ventilation and submit for public review and acceptance as standards practice Maximize attic contribution to energy savings through integration of key strategies into Next Generation Attic PCM, cool roofs (IRR), above sheathing ventilation and radiant barriers combined into Next Generation Attic Computer Tool Benchmarking

26 MCA Field Testing of Painted Metal ESRA Lane Installation Radiant Barrier Insulation 10 1 Offset from deck 4.0-in, dual air channel Low-e foil on deck facing up Hardy Board (0.5-in) 2 11 Offset from deck 0.75-in 4-in using clips clips Backer on on metal underside No insulation above deck 12 Direct-to-Deck Offect from deck (option 2-in for using variable clips space) Low-e paint on on underside No insulation above deck 13 1 ventilation Low-e foil on deck facing up No insulation above deck Offset from deck 4.0-in, forced 14 Offset from deck 0.75-in using clips Backer on metal underside R-1.0 above deck 15 Offset from deck 0.75-in using clips Low-e paint on underside No insulation above deck 1 Roof and attic assemblies already under evaluation. 2 Hardy board used to separate two air channels above roof deck. 26

27 Roof with ¾- and 2-in airspace yield similar roof heat flows to roof with 4-in airspace 27

28 Roof with R-1 insulation placed above deck yields similar thermal performance to roof with ¾-in airspace above deck

29 AtticSIM II (Attic Simulation) Model k

30 1 st Generation Roof and Attic Painted metal roof (SR28E81, 4-in air gap, 2 Low-e, PCMs)

31 Advanced Attic with PCM Shaves Peak Demand and Reduces Night Sky Losses Peak Demand Reduction

32 Effect of Cool Color, Above-Sheathing Ventilation, PCMs, and Low-e Reflective Insulation Full System Integration July 28, 2006

33 Above Sheathing Ventilation Roofs Negate Heating Penalty

34 Cool Color painted metal with ASV, Low-e surface and PCM [2 nd Generation prototype] ESRA 2-in Air space IRR Shingle with RB Clay and Concrete tile with above deck EPS insulation 4-in Air space PCM Roof Conventional Shingle

35 Next Generation Attics (in progress)

36 Surface and Underside Temperatures of tooth and valley not affected by RB

37 OSB Deck Temperature Increases Sheathing 4 o F increase OSB Underside 15 o F increase

38 2 nd Generation Roof and Attic

39 Conventional Mass, Above-Sheathing Ventilation and Above Deck Insulation ECOSET SYSTEM Conventional thermal mass works well when combined with foam insulation placed above sheathing July 28, 2006

40 Energy Plus Simulation: PCM in Fiberglass Insulation Blown on Attic Floor About $1.30 per ft 2 of attic floor would be spent to increase thermal resistance of conventional blown-in fiberglass insulation

41 AtticSIM (Attic Simulation) Model ASTM C Standard For Estimating Heat Gain of Loss Through Ceilings Under Attics Roof Energy Balance Miller et al. (2007), Natural Convection Heat Transfer in Roofs with Above-Sheathing Ventilation. Florida Solar Energy Center

42 AtticSIM II Validations Asphalt Shingle (SR093E89) Ceiling Heat Flux

43 Asphalt Shingle (SR093E89) with radiant barrier facing attic space OSB with RB facing attic

44 AtticSIM II Validations Flat Concrete tile (SR13E83) on double batten system Ceiling Heat Flux

45 AtticSIM II Validations S-Mission Clay Tile (SR54E90) Heat flux through roof deck Direct-to-Deck

46 S-Mission Clay Tile (SR54E90) with 1¼-in EPS insulation on roof deck (Ecoset) Heat flux through roof deck

47 AtticSIM Simulations Include Duct System Summer Duct Loss Cools Attic Winter Duct Loss Heats Attic Leakage Out (4%) Leakage Out (4%) Leakage Out (4%) Supply (12 in OD) Leakage Out (4%) HVAC Leakage In (4%) Return (12 in OD) Supply Duct 309 ft 2 Return Duct 176 ft 2

48 AtticSim Duct Validation Petrie, T.W., Wilkes, K.E. et al. (1998), Effect of Radiant Barriers and Attic ventilation on Residential Attics and Attic Duct Systems: New tools for Measuring and Modeling. ASHRAE Transactions, June Predicted T ( o F) Predicted Duct Capacity (Btu/hr) Winter No RB Winter No RB Winter Winter RB RB Summer Summer No RB No RB Summer Summer RB RB Measured HVAC Capacity (Btu/hr) Measured T ( o F)

49 Equivalent R-Value of Ceiling Insulation for SR25E75 Roof with Inspected Ducts Zone 09: Attic Contains R-30 Insulation and AC Ducts with R-6 Insulation Annual Ceiling & Duct Load (kbtu/yr) Annual Ceiling & Duct Load (kbtu/yr) 20,000 20,000 18,000 18,000 16,000 16,000 14,000 14,000 12,000 12,000 10,000 10,000 8,000 8,000 6,000 6,000 4,000 4,000 2,000 2,000 $700 for 1400 ft 2 attic footprint by BNI (2008) Equivalent R-13 No Radiant barrier No Radiant barrier Radiant barrier Radiant barrier Insulation R-Value Insulation R-Value

50 Equivalent R-Value of Insulation for SR25E75 Roof with Inspected Ducts Zone 15: Attic Contains R-38 Insulation and AC Ducts with R-8 Insulation Annual Ceiling & Duct Load (kbtu/yr) Annual Ceiling & Duct Load (kbtu/yr) 35,000 35,000 30,000 30,000 25,000 25,000 20,000 20,000 15,000 15,000 10,000 10,000 5,000 5,000 $1200 for 1400 ft 2 attic footprint by BNI (2008) No Radiant barrier No Radiant barrier Radiant barrier Radiant barrier Equivalent R Insulation R-Value Insulation R-Value

51 Annual Cost of Ceiling and Duct Energy based on TDV 30-yr forecast of $0.145 per kbtu NG Zone 15: Attic Contains R-38 Insulation and AC Ducts with R-8 Insulation $600 $600 Present Value $ per year Present Value $ per year $500 $500 $400 $400 $300 $300 $200 $200 $100 $100 Annual Savings Annual Savings $47 $47 $0 $ Insulation R-Value Insulation R-Value

52 Radiant Barrier Yields Greater Return on Investment than ASV and or Low-E in Airspace Zone 15: Attic Contains R-38 Insulation and AC Ducts with R-8 Insulation Asphalt shingle SR10E75 NoRB 0.9 Asphalt shingle SR10E75 RB 0.05 Asphalt shingle SR50E75 NoRB 0.9 Asphalt shingle SR50E75 RB 0.05 Clay IRR tile 2-in EPS SR56E90 NoRB 0.9 Clay IRR tile 2-in EPS SR56E90 RB ,000 70,000 Heating and Cooling TDV Load TDV Load (kbtu NG/yr) 60,000 50,000 40,000 30,000 20,000 Attic Footprint 1250 ft 2 ( 115m 2 ) 10, Attic Floor (R-Value)

53 Retrofit Prototype Roof on Pre-1980 Construction Requires Attic Work

54 Prototype Roof on Post-1980 Construction Yields Energy Savings of about 5 MBtu NG /yr Improving Ductwork $15 to $45/yr Prototype Roof Savings $15 to $40/yr Max Savings $146/yr

55 Space conditioning energy attributable to attics reduced almost by 50% of Post-1980 Constriuction Ranking of Roof and Attic Strategies Annual Cooling Load $ ,400 1,400 $ ,200 1,200 $ ,000 1,000 $ $ $ $5.00 $ ,301 1,301 $ ,069 1,069 $23.66 Attic Footprint 1250 ft 2 ( 115m 2 ) $ $ $16.22 Base SR10E75 Base SR10E75 Base SR10E75 SR10E75, RB SR10E75, RB RB SR25E75, RB, IRR SR25E75, SR25E75, RB, RB, IRR IRR SR28E75, RB, IRR, ASV(1") SR28E75, SR28E75, RB, RB, IRR, IRR, ASV(1") ASV(1") Base + Ecoset Base + Ecoset Base + Ecoset (KWh) TDV NPV (KWh) ($/square yr)

56 CONCLUSIONS Ductwork in Attics Are the Predominant Energy Loss Radiant Barrier provides best opportunity for return on Investment Smart Integration yields positive gains in roof and attic performance (regional design) Reflective surfaces (low-e) Conventional insulations PCM insulations Above Sheathing Ventilation Cool Color Roofs GOAL Reduce space conditioning attributable to attics by 50% of Building America regional benchmark (R50 Roof, R30 Wall.